linux-kernel - Re: [PATCH v4] sched/topology: Enable topology_span

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Message-ID: <81b11433-58ac-4a2c-a497-d6d91e330810@linux.microsoft.com>
Date: Fri, 7 Mar 2025 20:35:23 +0530
From: Naman Jain <namjain@...ux.microsoft.com>
To: Valentin Schneider <vschneid@...hat.com>, Ingo Molnar <mingo@...hat.com>,
 Peter Zijlstra <peterz@...radead.org>, Juri Lelli <juri.lelli@...hat.com>,
 Vincent Guittot <vincent.guittot@...aro.org>,
 Dietmar Eggemann <dietmar.eggemann@....com>,
 Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>,
 Mel Gorman <mgorman@...e.de>
Cc: stable@...r.kernel.org, linux-kernel@...r.kernel.org,
 Steve Wahl <steve.wahl@....com>,
 Saurabh Singh Sengar <ssengar@...ux.microsoft.com>, srivatsa@...il.mit.edu,
 K Prateek Nayak <kprateek.nayak@....com>,
 Michael Kelley <mhklinux@...look.com>,
 Shrikanth Hegde <sshegde@...ux.ibm.com>
Subject: Re: [PATCH v4] sched/topology: Enable topology_span_sane check only
 for debug builds



On 3/6/2025 10:18 PM, Valentin Schneider wrote:
> On 06/03/25 11:23, Naman Jain wrote:
>> diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
>> index c49aea8c1025..666f0a18cc6c 100644
>> --- a/kernel/sched/topology.c
>> +++ b/kernel/sched/topology.c
>> @@ -2359,6 +2359,13 @@ static bool topology_span_sane(struct sched_domain_topology_level *tl,
>>   {
>>        int i = cpu + 1;
>>
>> +	/* Skip the topology sanity check for non-debug, as it is a time-consuming operation */
>> +	if (!sched_debug()) {
>> +		pr_info_once("%s: Skipping topology span sanity check. Use `sched_verbose` boot parameter to enable it.\n",
>> +			     __func__);
> 
> FWIW I'm not against this change, however if you want to add messaging
> about sched_verbose I'd put that in e.g. sched_domain_debug() (as a print
> once like you've done here) with something along the lines of:
> 
>    "Scheduler topology debugging disabled, add 'sched_verbose' to the cmdline to enable it"


Thank you so much for reviewing.
Please correct me if I misunderstood. Are you proposing below change?

--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -2361,7 +2361,7 @@ static bool topology_span_sane(struct 
sched_domain_topology_level *tl,

         /* Skip the topology sanity check for non-debug, as it is a 
time-consuming operation */
         if (!sched_debug()) {
-               pr_info_once("%s: Skipping topology span sanity check. 
Use `sched_verbose` boot parameter to enable it.\n",
+               pr_info_once("%s: Scheduler topology debugging disabled, 
add 'sched_verbose' to the cmdline to enable it\n",
                              __func__);
                 return true;
         }


Regards,
Naman

> 
>> +		return true;
>> +	}
>> +
>>        /* NUMA levels are allowed to overlap */
>>        if (tl->flags & SDTL_OVERLAP)
>>                return true;
>> --
>> 2.34.1